29" = 700c which is the standard road wheel diameter (and therefore the standard for CX), so if you go with that size, you'll have lots of options on CX specific tires and wheels that you might not find in the other sizes. (Although the rear dropout spacing is usually different between CX and MTB, so just keep that in mind when buying wheels).

From MTB perspective, the difference between 26", 27.5" and 29" seems to be mostly personal preference and isn't necessarily related to your size or inseam. You should have no problem fitting on any of them, assuming you buy the correct sized frame. I'm shorter than you and have no problem on a 29er with suspension for mountain biking.